U.S. Pat. application Ser. No. 578,866, filed on Feb. 10, 1984, now U.S. Pat. No. 4,571,990 discloses a method for measuring the rate of air flow in the intake pipe of an internal combustion engine. This method uses a flow metering device which is insensitive to the direction of flow. In order to ensure continued accuracy of the measured air quantity drawn in by suction by the internal combustion engine also in the event of a change in the direction of flow, as it may occur with pulsations in the intake pipe, this application discloses various methods for determining the points in time of flow reversal. The determination of these reversal points is based on specific physical relationships between: the flow metering signal, differential pressures, the occurrence of extreme values in the flow metering signal and the gradient of the flow metering signal.
It has been shown, however, that these methods do not yield optimum results for any type of internal combustion engine; moreover, they may even provide incorrect results by way of disturbances superposed on the measured value sensor output signal.